Super Moderator

As to (1), from 12 to release, you don't want a lot of specific instructions on what to do with the arm. Pitching is a fluid motion. If you start telling the pitcher exactly where the arm has to be at every position from 12 to release, then the pitcher will lose the flow and will start thinking, "Do A. Now do B. Now do C."

So, generally, the pitcher does thousands (literally, thousands) of half frames (pitcher is open, with arm up as high as possible, slight bend in elbow, then pitcher throws but does not close her body). The instructor is checking the position as 12, the follow through, and the arm circle.

(2) The hand is not on top of the ball as it goes from 12 O'clock to release. Here is Finch:

The hand is on the side of the ball. For a fastball, the hand rotates from her so that the palm is pointing toward home plate. For a riseball, the hand continues in this position.

(3) You don't teach "where the hand is when you start putting spin on the ball". You explain how to put spin on the ball. The pitcher learns to put spin on the ball by doing "flips" with only enough arm motion as is required to spin the ball. Then, you integrate that motion into half frames, and then eventually into the full pitching motion.